Science China Materials最新文献

The development of low-cost, highly active platinum (Pt)-based electrocatalysts for oxygen reduction reaction (ORR) is crucial for widespread applications of fuel cells. An effective approach lies in alloying Pt with non-noble transition metals to modulate the physicochemical state of the Pt surface. However, fundamental challenges remain in understanding the structure-performance relationship due to the complexity of composition, crystal type, and surface structure during the alloying process. In this study, we synthesized a series of PtCo bimetallic solid solutions with varying ratios using a liquid-phase synthesis method. By exploiting the characteristics of solid solutions, the resulting PtCo bimetallic alloy maintains the face-centered cubic crystal structure of pure platinum, minimizing the complexities introduced during alloying and facilitating mechanism analysis. Furthermore, under controlled alloy composition and crystal structure, we investigated the dependence of the electrocatalytic activity for the oxygen reduction reaction on the surface strain of the platinum catalyst. The S-PtCo-SNPs cathode designed accordingly endows both proton exchange membrane fuel cell (PEMFC) (2.08 W cm⁻² at 4 A cm⁻²) and Zn-air battery (ZAB) (143.1 mW cm⁻² at 214.5 mA cm⁻²) with outstanding performance.

Compared with the inherent brittleness of bulk silicon (Si) at ambient temperature, the nanosized Si materials with very high strength, plasticity, and anelasticity due to size effect, are all well-documented. However, the ultimate stretchability of Si nanostructure has not yet been demonstrated due to the difficulties in experimental design. Herein, directly performing in-situ tensile tests in a scanning electron microscope after developing a protocol for sample transfer, shaping and straining, we report the customized nanosized Si mechanical metamaterial which overcomes brittle limitations and achieves an ultra-large tensile strain of up to 95% using the maskless focused ion beam (FIB) technology. The unprecedented characteristic is achieved synergistically through FIB-induced size-softening effect and engineering modification of mechanical metamaterials, revealed through analyses of finite element analysis, atomic-scale transmission electron microscope characterization and molecular dynamics simulations. This work is not only instructive for tailoring the strength and deformation behavior of nanosized Si mechanical metamaterials or other bulk materials, but also of practical relevance to the application of Si nanomaterials in nanoelectromechanical system and nanoscale strain engineering.

The conversion of carbon dioxide (CO₂) to the reduced chemical compounds offers substantial environmental benefits through minimizing the emission of greenhouse gas and fostering sustainable practices. Recently, the unique properties of metal-organic frameworks (MOFs) make them attractive candidates for electrocatalytic CO₂ reduction reaction (CO₂RR), providing many opportunities to develop efficient, selective, and environmentally sustainable processes for mitigating CO₂ emissions and utilizing CO₂ as a valuable raw material for the synthesis of fuels and chemicals. Here, the recent advances in MOFs as efficient catalysts for electrocatalytic CO₂RR are summarized. The detailed characteristics, electrocatalytic mechanisms, and practical approaches for improving the electrocatalytic efficiency, selectivity, and durability of MOFs under realistic reaction conditions are also clarified. Furthermore, the outlooks on the prospects of MOF-based electrocatalysts in CO₂RR are provided.

We report a novel benzoxazole derivative, 1,4-bis(benzo[d]oxazol-2-yl)naphthalene (BBON), exhibiting exceptional multifunctional properties for advanced optoelectronic applications. BBON crystals demonstrate remarkable multidirectional bending and twisting at room temperature and retain elasticity under extreme conditions, such as exposure to liquid nitrogen, showcasing their durability. These crystals can be crafted into complex mesh and lantern shapes, highlighting their versatility for flexible and wearable technologies. Under high pressure, BBON exhibits significant piezochromic shifts, with the emission wavelength shifting from 477 to 545 nm upon pressure increase. BBON crystals, with a high quantum yield of 72.26%, exhibit excellent optical waveguide performance: 0.38 dB/cm when straight and 0.56 dB/cm when bent. These properties make them ideal for smart sensors and flexible electronic devices. Single-crystal analyses reveal that molecular stacking and intermolecular interactions are crucial to their elastic and piezochromic properties, providing insights for the design of future responsive materials.

The inherent limitations of hydrogels, such as low electrical conductivity and inadequate sensitivity, present considerable challenges in flexible electronic applications. To address these issues, we proposed an innovative synthesis technique that synergistically leveraged the nanoscale properties of the conductive fillers including one-dimensional polyaniline and two-dimensional reduced graphene oxide to fabricate hydrogels with exceptional conductivity. This advanced hydrogel exhibited an extraordinary sensitivity with a gauge factor of 27.55, impressive electrical conductivity (7.2 mS/cm), and outstanding stability. Additionally, the hydrogel demonstrated excellent self-adhesion and robust self-healing properties, attributed to its abundant catechol functionalities, hydrogen bonding interactions, and π-π stacking. Consequently, the flexible, strain-sensitive, self-powered sensors derived from these hydrogels displayed unparalleled sensing performance, positioning them as highly promising candidates for advanced human-computer interaction systems and sophisticated information transmission applications.

Black phosphorus (BP) has been regarded as a promising two-dimensional semiconductor due to its excellent properties including high carrier mobility and widely tunable direct bandgap. Despite extensive interest as well as research progress, the preparation of large-size and high-quality BP single crystal in high throughput still remains challenging. Here, a facile growth of centimeter-sized BP single crystal flakes with dozens of throughput per batch is achieved by using bidirectional vapor transport (BVT) method. High crystal quality is confirmed by structural and spectrum characterizations, with an X-ray diffraction rocking curve peak half-height width of only 0.02°. The as-grown BP single crystal flake with smooth cleavage plane can be easily exfoliated into large scale nanosheets. Field-effect transistors fabricated based on the BP by such approach show excellent performance including reliable carrier mobility up to 1150 cm² V⁻¹ s⁻¹ and on/off current ratio of ~10⁶ at 15 K. This approach is also applicable to various doped-BP, such as As-BP, Se-BP, Te-BP, etc. The ability to grow centimeter-sized BP single crystal flakes in high yield will accelerate the research and applications of BP-based electronics and optoelectronics.

High-temperature stability of organic field-effect transistors (OFETs) is critical to ensure its long-term reliable operation under various environmental conditions. The molecular packing of donor-acceptor (D-A) conjugated polymers is closely related to the electrical performance stability in OFETs. Herein, we choose poly[[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)] as a modal system to reveal the relationship between the molecular stacking and electrical stability in high-temperature environment. The results demonstrate that the films with D-A moieties in alternate stacking have better electrical thermal stability compared to normal donor-donor (D-D) stacking. The D-A stacking configuration alternates donor and acceptor units along the out-of-plane direction, while the D-D stacking involves D-D and A-A stacking separately. The structural transition from D-D to D-A is captured at a treated temperature range of 225–250°C. Owing to the tighter packing arrangement along the π-π and lamellar directions, the electron mobility of the D-A stacked films reaches up to 0.23 cm²/V·s, a 50% increase as compared to the D-D stacking films. Furthermore, the D-A stacked films indicate superior electrical performance stability with mobility retaining 100% at 250°C during high-temperature cycling tests. This result highlights that the manipulation of conjugated polymer closely stacked structures can significantly enhance the thermal stability and durability of semiconductor devices.

Surface modification using biomaterials is crucial for constructing bioactive interfaces that can control cell behavior, regulate biological processes, and interact with specific biomolecules. Tannic acid (TA), a naturally derived polyphenol, is of particular interest due to its ability to complex ions, facilitating the fabrication of coordination networks through self-assembly of TA and metal ions, known as metal-phenolic networks (MPNs). These MPNs can form stable, yet dynamic structures that can be further engineered or tailored for specific therapeutic needs. Synthetic TA-based MPN complexes have been constructed to modify diverse biointerfaces due to their unique physiochemical properties, including universal adhesion, pH responsiveness, controllable size and stiffness, ease of preparation, and excellent biocompatibility, which are highly advantageous for various biological applications, particularly in cell therapy. This review explores the synthesis, properties, and applications of TA-based MPNs in the context of therapeutic cells, including bacteria, yeast, and mammalian cells. Key aspects such as biocompatibility, biodegradability, the ability to modulate cellular environments, and clinical translation are discussed, highlighting the potential of TA-based MPNs to advance cell therapy.

For luminescent materials, negative thermal quenching (NTQ), characterized by an increase in the luminescent intensity with temperature, has a large potential in lighting and display technologies. However, leveraging NTQ in metal halide perovskites is challenging, and the mechanism is not well understood. Herein, by utilizing low-temperature photoluminescence, persistent luminescence and thermoluminescence, the origins of NTQ in CsPbBr₃ microspheres are systematically studied, which pertain to the liberation of carriers from shallow trap states. Experimental and theoretical investigations reveal that the energy of these shallow defect states is approximately 0.135 eV beneath the conduction band. A rapid thermal treatment increases the density of these shallow traps and amplifies the NTQ effect, resulting in an enhancement of room-temperature photoluminescence by more than 60% compared to that at 150 K. The process also reduces the threshold for amplified spontaneous emission to about 45 W/cm². Our findings not only provide a deeper understanding of the NTQ phenomenon in CsPbBr₃ microspheres but also open new avenues for enhancing the performance of perovskite optoelectronic devices through energy state regulation.